The present invention relates to a suspension apparatus mounted on a vehicle such as an automobile, and preferably used to absorb vibrations of the vehicle.
Generally, a vehicle such as a four-wheeled vehicle includes a shock absorber disposed between the vehicle body side and the respective wheel sides. Some of such shock absorbers can adjust its damping force by utilizing an actuator, and one known type of suspension apparatuses is configured to variably control the damping force characteristic according to, for example, the posture of the vehicle body and the state of vertical vibrations when the vehicle is running (for example, refer to Japanese Patent Application Public Disclosure No. H07-232530).
Such a suspension apparatus according to the conventional technique calculates a vertical absolute speed based on a signal from a G sensor, which detects a vertical acceleration of the vehicle body, and variably adjusts the damping force characteristic of the shock absorber according to the calculated absolute speed as well as determines whether a road surface on which the vehicle is currently running is in a good condition or a bad condition based on the signal from the G sensor. The suspension apparatus sets a small dead zone if the road surface is in a good condition while sets a large dead zone if the road surface is in a bad condition, whereby the suspension apparatus can reduce the influence of frequent vertical vibrations generated from the travel on the bad road, thereby maintaining the ride quality even when the vehicle is running on the bad road.